Article

Impacts of extreme ocean warming on the early development of a marine top predator: The Guadalupe fur seal

Authors:
  • Cientinela del Mar A.C. Non-profit organization
  • CONACYT - Ensenada Center for Scientific Research and Higher Education
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Abstract

From fall 2013 through 2015, a large-scale, multi-year warm water anomaly occurred in the northeast Pacific Ocean. The phenomenon had negative impacts on some oceanic predators, including higher mortalities and poor body conditions. We studied the effect of this warm water anomaly on the weight gain of Guadalupe fur seal(Arctocephalus philippii townsendi) neonates off the coast of the Baja California Peninsula, Mexico. Individuals were captured, marked, and weighed every 13–15 days, up to 60 days of age, during the early nursing seasons (mid-June to mid-August) of 2014–2016 at this subspecies’ only reproductive colony, located on Guadalupe Island. The body weight was measured at each capture and recapture. A hierarchical Bayesian model was used to explore the impact of sea surface temperature (SST) anomalies on the neonates’ weights. The hierarchical structure included connected models for the spring-summer SST trend around the colony, the neonatal body weight gain with age, and the relationship between the anomalies of both variables. Marked neonates were also tracked in order to estimate survival rates during first two months of age. Overall, positive SST anomalies had a negative effect on neonatal body weight gain. The northeast Pacific Marine Heatwave precipitated the lowest weights at birth and the slowest weight gain in 2014, as well as low weights and the lowest survival rate in 2015, likely due to the persistence of the warm anomalies. The evident sensitivity of Guadalupe fur seal neonates to regional warming conditions highlights their vulnerability under scenarios of climate change, which could impede this subspecies’ continued recovery from near extinction.

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Applied Hierarchical Modeling in Ecology: Distribution, Abundance, Species Richness offers a new synthesis of the state-of-the-art of hierarchical models for plant and animal distribution, abundance, and community characteristics such as species richness using data collected in metapopulation designs. These types of data are extremely widespread in ecology and its applications in such areas as biodiversity monitoring and fisheries and wildlife management. This first volume explains static models/procedures in the context of hierarchical models that collectively represent a unified approach to ecological research, taking the reader from design, through data collection, and into analyses using a very powerful class of models. Applied Hierarchical Modeling in Ecology, Volume 1 serves as an indispensable manual for practicing field biologists, and as a graduate-level text for students in ecology, conservation biology, fisheries/wildlife management, and related fields. Provides a synthesis of important classes of models about distribution, abundance, and species richness while accommodating imperfect detection Presents models and methods for identifying unmarked individuals and species Written in a step-by-step approach accessible to non-statisticians and provides fully worked examples that serve as a template for readers' analyses Includes companion website containing data sets, code, solutions to exercises, and further information
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Male mammals show a diverse array of mating bonds, including obligate monogamy, unimale and group polygyny and promiscuity These are associated with a wide variety of different forms of mate guarding, including the defence of feeding and mating territories, the defence of female groups and the defence of individual receptive females. Female mating bonds include long-term monogamy, serial monogamy, polyandry and promiscuity Both male and female mating behaviour varies widely within species. Variation in male mating behaviour is related to the effect of male assistance in rearing young and to the defensibility of females by males. The latter is, in turn, related to female ranging behaviour and to the size and stability of female groups. Much of the variation in mammalian mating bonds and systems of mate guarding can be attributed to differences in these three variables.
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We studied the influence of sex of pup, maternal age, birth date of pup, number of foraging trips, and the mean duration of foraging trips at sea and nursing visits ashore on the growth and mass at weaning of pups of Antarctic fur seals (Arctocephalus gazella) during austral summers of 1988-1990. Although growth and mass at weaning were highly correlated, they were not related to maternal characteristics in 1988 or 1989. However, in 1990 there was a negative relationship between growth of pups and mean duration of foraging trips. Growth rates of males and females varied considerably between 1972 and 1991 and appeared to decline from 1984 through 1990. Methods used to collect and weigh the pups influenced the nature and magnitude of sex differences in estimated growth rates. Growth rates of male and female pups did not differ when weighed serially (same individuals weighed throughout lactation), but males grew faster than females when weighed cross-sectionally (different individuals weighed throughout lactation). Based on our results of pairs of mothers and pups followed over the lactation period, maternal investment was greater in males than females because males were heavier at birth and older at weaning than females and not because of any differential growth between the sexes. Mothers appear to have to work longer, but not harder, to wean males than females. Under the favorable feeding conditions that usually exist, individual differences in the growth of pups are most likely influenced by variation in foraging efficiency of mothers.
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In order to compensate for the resource demands of reproduction, organisms usually increase the amount of total food resources available. This may be achieved by different tactics of resource use that also include foraging decisions. Two such general tactics are discussed in this paper under the concepts of capital and income breeding. These are defined mainly from the temporal distribution of resource acquisition relative to resource use. A capital breeder acquires its resources in advance and store them endogenously or exogenously until they are needed to supply aspects of offspring production. An income breeder, on the other hand, adjusts its food intake concurrently with breeding, without reliance on stores. In a perfectly predictable environment without limited resources, income breeding is the best option since capital breeders may have to pay a number of energetic and demographic costs for their stored resources. However, under unpredictable food conditions, food/time limitations, and risky fora
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1. The reproductive performance of female Antarctic fur seals was examined in relation to age, reproductive experience and environmental variation over 10 consecutive years (1983-92) at Bird Island, South Georgia. 2. The age at which females first gave birth varied from 3 to 6 years; over 90% of these females were 3 or 4 years of age. We found no evidence to suggest that age at primiparity had significant effects on subsequent reproduction; however, 3-year-old primiparae were less likely to be seen in subsequent years than 4-year-old primparae which may indicate a cost, in terms of survival, for females that first give birth at an early age. 3. Age-specific reproductive rates increased rapidly from ages 2 to 6 years, reached a peak of 0.80 at 7-9 years, remained above 0.75 until 11 years and then began to decline with increasing age. 4. The mean duration of foraging trips in the current year (which was used as a measure of the availability of food resources) consistently improved models of the likelihood of pupping and of weaning success. When these trips were long (indicating reduced local food resources), females returned to the breeding beaches later, fewer females pupped, they gave birth to lighter pups and weaning success was reduced. 5. The reproductive performance of older, experienced Antarctic fur seals was greater than that of younger, inexperienced animals because they had higher natality rates, gave birth to heavier pups earlier in the season, had greater weaning success and were more likely to pup the next season.
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Summary 1. A major hypothesis of life history theory is that early development conditions affect future survival and reproductive success. However, although a growing number of studies have addressed this question, many of them are taxonomically biased, thereby impeding the generalization of this hypothesis. 2. This study examines the factors influencing post-weaning survival in five weaned cohorts of subantarctic fur seal pups from Amsterdam Island, southern Indian Ocean. It used mark-recapture data from 7 consecutive years of different environmental conditions. 3. The cohort return rate varied from 45% to 74% of weaned pups, depending on the year of weaning. In each cohort, 96% of weaned pups returned between 3 and 6 years of age, and none of the factors examined seemed to influence this timing pattern. The probability of survival to this first return was negatively related to sea-surface temperature anomalies (SSTa) of the 6 months following the weaning process. It increased with pup preweaning growth rate and differed between the sexes. Females' survival rate was significantly higher than males', except during years of extreme SSTa, where no difference was detected. 4. The juvenile state represented young individuals after their first return on their native island. Annual juvenile tag loss rate was constant at 0·217 (SE = 0·027), whereas temporary emigration rate varied over cohorts and was higher in males 0·423 (SE = 0·035) than in females 0·170 (SE = 0·012). This dispersion pattern may be prolonged in some cases, as the yearly immigration probability was constant at 0·290 (SE = 0·065). 5. Taking into account tag loss and temporary emigration, the estimated yearly survival probability of juveniles was 0·964 (SE = 0·022). This value was unrelated to any tested oceanographic or individual parameter including sex. 6. Results support the hypothesis that early development traits affect short-term post-weaning survival. However, no long-term effect of maternal postnatal investment was detected after the first return to the native island. Results also indicate that the effect of early development traits on survival interacts with environmental conditions encountered shortly after independence of individuals.
Article
1In order to estimate the effect of weaning mass and body condition on the post-weaning survival of grey seal pups from the Isle of May, Scotland in 1998 during their first year of life, a simultaneous analysis of live resighting and dead recovery mark–recapture data was used. A new type of tag was employed which allowed individuals to be identified when resighted alive (Hall, Moss & McConnell 2000) as well as when found dead.2The probability of post-weaning survival to age 1 increased with body condition at weaning and differed between the sexes. Regardless of pup condition and time of year, the odds of survival for female pups over a 2-month interval was estimated to be 3·37 (SE = 1·30) times higher than for males. Regardless of sex, a 1 standard deviation increase in pup condition was estimated to increase the odds of survival by a factor of 1·422 (SE = 0·226). For a male pup in average condition (0·41 kg cm−1) the estimated annual survival after adjusting for tag-loss was 0·193 (SE = 0·084); for a female pup in average condition (0·39 kg cm−1) it was 0·617 (SE = 0·155).3The effect of condition at weaning on survival was significantly greater for male pups than for females. This implies that high quality females should invest more heavily in their male pups because the marginal return, in terms of increased reproductive value, from any additional expenditure is twice that for females. Male pups in our sample were significantly heavier at weaning and in better condition than female pups. However, this does not provide conclusive support for our predictions, because we could not control for the effects of maternal size on weaned mass.